11.6 Indigenous Bacterial Addition
Using the microcosm subsystem, a combination of Chlorella vulgaris (producer),
Cyclidium glaucoma (consumer), Pseudomonas putida (decomposer), the microbial
pesticide, Bacillus thuringiensis subsp. aizawai KH as a nonindigenous bacterium,
and Escherichia coli HB101/pBR325 as a non-transmissible plasmid-containing
indigenous bacterium was added to the microcosm after culturing began, with 10
8
cells/mL on the 16th day (during the stationary phase). Both Bacillus thuringiensis
subsp. aizawai KH and Escherichia coli HB101/pBR325 were preyed upon by the
protozoan Cyclidium glaucoma after addition and decreased to a population of 10
5
cells/mL (after addition the 14th day) by the 30th day. With respect to the predation
characteristics of Cyclidium glaucoma, a similar result was provided in the predatorprey interaction test, and it was revealed that both nonindigenous bacteria were
suitable food sources. The surviving population came to have more than ten times
the abundance of the microcosm N-system and was comprised of a greater diversity
of biota on the 30th day (after addition on the 14th day). This indicates that the
ecosystem is composed of complex interactions and that the interactions become
more complicated with the introduction of nonindigenous organisms. Additionally,
after mathematical simulation of the Escherichia coli HB101/pBR325 addition
system, it was revealed that laboratory findings and simulation results were in
good agreement with one another by treating the bacteria that were not preyed
upon as a different variable than those that were preyed upon. The effects of bacterial
cohesiveness and shape were large and greatly accounted for the differences between
the predation properties of Cyclidium glaucoma at both high and low concentrations
of Escherichia coli HB101/pBR325.
11.7 Irradiation
The influence of continuous gamma ray irradiation on the microcosm subsystem
comprised of the bacterial decomposer, Escherichia coli; the ciliate predator, Tetrahymena thermophila; and the flagellate producer, Euglena gracilis, was evaluated.
In the control system, the abundance values of Escherichia coli, Euglena gracilis,
and Tetrahymena thermophila were constant at 10
6 , 3 Â 10
5 , and 10
3 cells/mL,
respectively, during the stationary phase. In contrast, the cell count of Escherichia
coli decreased when they were irradiated for 56 days over more than one column,
with both 10 Gy/day and 23 Gy/day, and some Tetrahymena thermophila also
perished. No influence was observed for Euglena gracilis at 10 Gy/day, but there
was a slight decrease in their abundance at 23 Gy/day. In contrast, in the microcosm
N-system, only bacteria decreased at 10 Gy/day, and bacteria and Lecane sp.
decreased, and Tolypothrix sp. increased at 23 Gy/day. Therefore, it may be said
that the microcosm N-system exhibited greater resistance to continuous gamma
radiation in comparison with the microcosm subsystem. Because these systems
200
Y. Inamori et al.
Using the microcosm subsystem, a combination of Chlorella vulgaris (producer),
Cyclidium glaucoma (consumer), Pseudomonas putida (decomposer), the microbial
pesticide, Bacillus thuringiensis subsp. aizawai KH as a nonindigenous bacterium,
and Escherichia coli HB101/pBR325 as a non-transmissible plasmid-containing
indigenous bacterium was added to the microcosm after culturing began, with 10
8
cells/mL on the 16th day (during the stationary phase). Both Bacillus thuringiensis
subsp. aizawai KH and Escherichia coli HB101/pBR325 were preyed upon by the
protozoan Cyclidium glaucoma after addition and decreased to a population of 10
5
cells/mL (after addition the 14th day) by the 30th day. With respect to the predation
characteristics of Cyclidium glaucoma, a similar result was provided in the predatorprey interaction test, and it was revealed that both nonindigenous bacteria were
suitable food sources. The surviving population came to have more than ten times
the abundance of the microcosm N-system and was comprised of a greater diversity
of biota on the 30th day (after addition on the 14th day). This indicates that the
ecosystem is composed of complex interactions and that the interactions become
more complicated with the introduction of nonindigenous organisms. Additionally,
after mathematical simulation of the Escherichia coli HB101/pBR325 addition
system, it was revealed that laboratory findings and simulation results were in
good agreement with one another by treating the bacteria that were not preyed
upon as a different variable than those that were preyed upon. The effects of bacterial
cohesiveness and shape were large and greatly accounted for the differences between
the predation properties of Cyclidium glaucoma at both high and low concentrations
of Escherichia coli HB101/pBR325.
11.7 Irradiation
The influence of continuous gamma ray irradiation on the microcosm subsystem
comprised of the bacterial decomposer, Escherichia coli; the ciliate predator, Tetrahymena thermophila; and the flagellate producer, Euglena gracilis, was evaluated.
In the control system, the abundance values of Escherichia coli, Euglena gracilis,
and Tetrahymena thermophila were constant at 10
6 , 3 Â 10
5 , and 10
3 cells/mL,
respectively, during the stationary phase. In contrast, the cell count of Escherichia
coli decreased when they were irradiated for 56 days over more than one column,
with both 10 Gy/day and 23 Gy/day, and some Tetrahymena thermophila also
perished. No influence was observed for Euglena gracilis at 10 Gy/day, but there
was a slight decrease in their abundance at 23 Gy/day. In contrast, in the microcosm
N-system, only bacteria decreased at 10 Gy/day, and bacteria and Lecane sp.
decreased, and Tolypothrix sp. increased at 23 Gy/day. Therefore, it may be said
that the microcosm N-system exhibited greater resistance to continuous gamma
radiation in comparison with the microcosm subsystem. Because these systems
200
Y. Inamori et al.